Milwaukee battery M18 B4 4.0 Ah

Provides up to 2 times longer operating time, up to 20% more power and up to 2 times longer battery life compared to other lithium-ion technologies and/or previous MILWAUKEE® battery technology (results depend on the tool and application)
REDLITHIUM™ battery protection with REDLINK™ digital overload protection to prevent the user from damaging the battery tool in harsh conditions.
Individual battery monitoring – ensures optimal charging and discharging to maximize battery life
The battery's durable metal frame construction and shock-absorbing separators prevent malfunctions caused by excessive vibration or dropping.
The corresponding protection system directs water away from the electronics and the battery
Can be used in extreme temperatures up to -20 °ºC without affecting operating time or battery life
The charge level indicator on the battery helps to use the battery with maximum efficiency